Android中Intent传递对象的两种方法Serializable,Parcelable

2019-12-10 19:14:10王振洲

下面看Parcelable的传递:

实现Parcelable一般需要4个步骤:

1)implements Parcelable

2)重写writeToParcel方法,将你的对象序列化为一个Parcel对象,即:将类的数据写入外部提供的Parcel中,打包需要传递的数据到Parcel容器保存,以便从 Parcel容器获取数据

3)重写describeContents方法,内容接口描述,默认返回0就可以

4)实例化静态内部对象CREATOR实现接口Parcelable.Creator

public static final Parcelable.Creator<T> CREATOR

注:其中public static final一个都不能少,内部对象CREATOR的名称也不能改变,必须全部大写。需重写本接口中的两个方法:createFromParcel(Parcel in) 实现从Parcel容器中读取传递数据值,封装成Parcelable对象返回逻辑层,newArray(int size) 创建一个类型为T,长度为size的数组,仅一句话即可(return new T[size]),供外部类反序列化本类数组使用。

简而言之:通过writeToParcel将你的对象映射成Parcel对象,再通过createFromParcel将Parcel对象映射成你的对象。也可以将Parcel看成是一个流,通过writeToParcel把对象写到流里面,在通过createFromParcel从流里读取对象,只不过这个过程需要你来实现,因此写的顺序和读的顺序必须一致。

具体:

1.新建Book的实体类:

Book.java:

package com.example.objecttrandemo; 
import android.os.Parcel; 
import android.os.Parcelable; 
public class Book implements Parcelable{ 
private String bookName; 
private String author; 
private int publishTime; 
public String getBookName() { 
return bookName; 
} 
public void setBookName(String bookName) { 
this.bookName = bookName; 
} 
public String getAuthor() { 
return author; 
} 
public void setAuthor(String author) { 
this.author = author; 
} 
public int getPublishTime() { 
return publishTime; 
} 
public void setPublishTime(int publishTime) { 
this.publishTime = publishTime; 
} 
//Internal Description Interface,You do not need to manage 
@Override 
public int describeContents() { 
return 0; 
} 
//give some attention to the oder betwwen writeToParcel and createFromParcel 
@Override 
public void writeToParcel(Parcel parcel, int flags){ 
parcel.writeString(bookName); 
parcel.writeString(author); 
parcel.writeInt(publishTime); 
} 
public static final Parcelable.Creator<Book> CREATOR = new Creator<Book>() { 
@Override 
public Book[] newArray(int size) { 
return new Book[size]; 
} 
@Override 
public Book createFromParcel(Parcel source) { 
Book mBook = new Book(); 
mBook.bookName = source.readString(); 
mBook.author = source.readString(); 
mBook.publishTime = source.readInt(); 
return mBook; 
} 
}; 
}